Why we compare prices at the middle of the order book

Every price the site compares is the middle of an exchange's order book: halfway between the highest offer to buy and the lowest offer to sell. Until 1 October, spot pages compared the last trade instead, the price most sites show. This is why that changed.

What an order book shows

An exchange's order book is two lists. The asks are offers to sell, lowest first; the bids are offers to buy, highest first. The best ask and the best bid are as close as the two sides get, and the gap between them is the spread. The middle of the book, the mid, is halfway across it.

A trade happens when someone takes one of those offers. A buyer takes the best ask and a seller the best bid, so each trade lands on one side of the spread or the other, and the last trade jumps between the two, as in the drawing at the top.

The last trade flickers

On a busy market the book moves between trades, so the last trade is often a tick or two outside the book as it stands now. On 1 October we counted, second by second for 30 seconds, how often each exchange's last Bitcoin trade sat outside its own best bid and ask.

Seconds out of 30 the last trade sat outside the book

• Hyperliquid26 of 30
• Bitget25 of 30
• Kraken18 of 30

Bitcoin spot, measured on 1 October 2026.

A price that flips every second while the market stands still isn't much to compare. Set side by side, last trades rank exchanges by when each last traded as much as by what each would charge now. The mid moves only when the book does.

A quiet market's last trade can be old

On a market that trades rarely, the last trade can be minutes or hours old. On 1 October, Nado's wrapped Apple token had last traded at $334.05 while its book stood at $332.07 to $332.77, so a buyer then paid $332.77, not $334.05. The trade was simply old. Its mid, $332.42, was where the market was.

When the middle means nothing

The mid only means something when the two sides are close. At 13:31 UTC on 1 October, Lighter's rhQQQ/USDC book had a bid at $741.98 and nothing for sale below $14,084. Its middle was $7,413: a price nobody was buying or selling at, in a book with almost nothing in it. The other six books on QQQ's page that minute were between 0.001% and 0.6% wide.

So a book whose best ask is more than 5% above its best bid has no price on the site. Its coin page shows a dash with a Thin tag that says why, and the index shows Thin and leaves it out of the lowest price and the gap. By 13:50 the rhQQQ book had closed up to $743.60 to $743.99, and its price was back.

What it means for the numbers you see

• Every price card says mid, and the chart's lines are mid prices.
• The gap and the lowest price on the index are between mids, so they compare where each market is now, not when it last traded.
• The mid isn't what an order pays. A buy fills at the ask and above, a sale at the bid and below, and a large order goes deeper into the book. The trade simulator on each coin page works out what an order of your size would get on each exchange.